Patent GB-745634-A (GB)
Title: Gas turbine driven compressor power plant
IPC: G05D23/02
Filed: 1952-03-03
Abstract: 745,634. Gas turbine plant. GARRETT CORPORATION. March 3, 1952 [March 13, 1951], No. 5521/52. Class 110(3) [Also in Group XXIX] In a gas turbine plant comprising a compressor supplying supplying air to a combustion chamber feeding the turbine and compressed air for external power purposes which is supplied with fuel by a pump having a valve-controlled by-pass around the pump, the valve is controlled in response to variations of compressor discharge pressure and by protective means responsive to a predetermined high temperature in the turbine exhaust. The compressor 12 driven by the gas turbine 11 supplies air to the combustion chambers 13' and 14 feeding the turbine and air to the distribution duct 28. Fuel is supplied to the combustion chambers 13, 14 from a pump 18, having a by-pass valve 25, through a shutbff valve 24. A starting motor 31 and overspeed switch 32 are also provided. The by-pass valve 25 comprises a casing 35 having a fixed wall 36 in which there is located an opening 38 controlled by a metering valve 45. The valve 45 which is mounted on spring loaded bellows 44 is connected by a stem 47 to a diaphragm 43. The space on one side of the diaphragm 43 is connected through an orifice 50 to the compressor discharge, the space between the diaphragm and the bellows 44 is open to atmosphere. The effective area of the bellows 44 is made equal to the area of the orifice 38 so that the valve 25 will maintain a substantially constant fuel to air ratio. The spring 46 ensures sufficient fuel pressure at the burners for ignition. Closure of the starting switch 51 causes current to flow from the battery A through conductor 80, contacts 76a, conductor 81, contacts 54 of the stop switch 53 conductor 82, contacts 78 and conductor 83 to relay 57 which closes its contacts 59 and connects the starter motor 31 to the battery B. At the same time the coil 69 of the holding relay 67 is energized from the conductor 81 through conductor 70, contacts 66 and 56. The relay 67 closes the contacts 68 to form a holding circuit for the relay 57. The switch 51 may now be released. The motor 31 accelerates the compressorturbine motor until the compressor discharge pressure reaches a predetermined value, when the bellows 71 expand and open the contacts 76a and close the contacts 76b. Closure of the contacts 76b allows current to flow from the battery A through conductor 85, contacts 68 conductor 86, contacts 54, conductor 81, contacts 76b and conductor 87 to the actuating solenoid of the valve 24 which is then opened and fuel flows to the combustion chambers 13, 14. At the same time the ignition coils 60, 61 are energized from the conductor 87 through conductor 88. contacts 77 and conductors 89, 90a and 90b. Thermcouples 62, 63 mounted in the hot gas ducts 15, 16 leading to the turbine are connected with opposed polarities in series with the actuating coil 64 of a differential relay 65 having normally closed contacts 66. Should one of the combustion chambers fail to light up a current will flow through the coil 64 and open the contacts 66; thus interrupting the circuit of the holding relay 67 which opens it contacts 68. This de-energizes the starting relay 57 which switches off the motor 31, the solenoid valve 24 which shuts of the fuel supply and the ignition coils 60, 61. The arrangement just described forms the subject-matter of Specification 745,719. If the ignition is normal in both combustion chambers, the compressor continues to build up pressure until the bellows 72 open contacts 77 which interrupt the energizing circuit of the ignition coils 60, 61. The plant continues to accelerate until the compressor discharge pressure is sufficient to operate the bellows 73 and open the contacts 78 which interrupt the circuit of the starting relay 57 and thus de-energize the starter motor 31. When the plant reaches the operating speed, the bellows 74 are operated to close the contacts 79 and energize the lamp 55. The overspeed switch 32 opens its contacts 56 in the event of excessive speed and de-energizes the holding relay 67 which then opens its contacts 68. The holding relay 67 may also be de-energized by operation of the stop switch 53. To prevent excessive turbine temperature during acceleration a thermostatic valve 91 as described in Specification 745,659 [Group XXIX], is mounted in the turbine exhaust. This valve controls the air pressure in the chamber 41 of the bypass valve 25 by allowing air to pass from the chamber 41 to atmosphere through a conduit 113 when a predetermined temperature is exceeded. The valve 91 also controls the flow of air through a conduit 115 and so controls the position of a throttle valve 119 in a distribution duct 28 by means of a servo-motor 120. The valve 91 is arranged to open the conduit 115 at a temperature, say 100‹F. lower than that at which it opens the conduit 113. It is stated that this allows the maximum temperature at the inlet of the turbine to be maintained regardless of the pneumatic load on the plant. The rotational speed of the plant is controlled by a pneumatic governor as described in Specification 745,658. This governor controls the air pressure in the chamber 41 through a conduit 144.